A Finite-Time Thermal Cycle Variational Optimization with a Stefan–Boltzmann Law for Three Different Criteria

Abstract

This work shows the power of the variational approach for studying the efficiency of thermal engines in the context of the Finite Time Thermodynamics (FTT). Using an endoreversible Curzon-Ahlborn (CA) heat engine as a model for actual thermal engines, three different criteria for thermal efficiency were analyzed: maximum power output, ecological function, and maximum power density. By means of this procedure, the performance of the CA heat engine with a nonlinear heat transfer law (the Stefan-Boltzmann law) was studied to describe the heat exchanges between the working substance and its thermal reservoirs. The specific case of the Müser engine for all the criteria was analyzed. The results confirmed some previous findings using other procedures and additionally new results for the Müser engine performance were obtained.

Impact Analysis of Intermediate Heat Carrier on Heat Transfer in Furnace

“…About 90.3% of heat flux on billet surface comes from radiation heat transfer [14][15][16], which depends on the temperature and emissivity of the heat transfer surface and their geometric structure and the properties of the surrounding gases [1]. According to the Stefan-Boltzmann law [17][18][19][20][21][22], the radiation heat exchange capacity is proportional to the fourth power of temperature difference, so the difference of temperature among surfaces has a significant impact on thermal radiation. In order to explore the impact rule of radiation heat transfer in heating furnace, scholars around the world carried out modeling research [23][24][25][26][27].…”

Is Carnot efficiency the upper bound for work extraction from thermal reservoirs?

“…However, there is quite a literature in this area (see, e.g. [8][9][10]; for a rather recent review, see [11]).…”